JPH0579927A - Optical measuring method for stress - Google Patents

Abstract

PURPOSE:To dispense with the wiring between a sensor detecting the stress strain of a structure and a measuring instrument and automate measurement. CONSTITUTION:Polarizing plates 3, 7 and 1/4 wavelength plates 4, 8 are fitted to an electronic camera 1 and a light source 6 respectively so that the light elastic effect of light elastic gauges 21, 21... stuck to the structure can be observed. The action of the electronic camera 1 is controlled by a computer 11. The RGB signals of the electronic camera 1 are stored in a frame memory 14, and the hue coordinates of the light elastic gauges 21, 21... on a screen are calculated by the computer 11. The strain quantity and stress are calculated via the displacement quantity of the light elastic gauges 21 from the hue coordinates of the reference color and stored in a memory device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stress measuring method, and more particularly to a stress measuring method for optically measuring stress strain of a structure.

[0002]

2. Description of the Related Art Conventionally, strain gauges have been used to measure stress and strain of structures. In this method, a strain gauge is attached to the surface of a structure to be measured, a change in electric resistance between both terminals of the strain gauge is measured, and the strain amount is converted.

[0003]

In the stress measuring method using the strain gauge described above, since the measuring instrument and the strain gauge are connected by the electric wire, if there are many measuring points,
The number of wires also increases, and wiring work and management become complicated.
Therefore, there is a technical problem to be solved in order to eliminate the wiring work and automatically collect the data to reduce the material and save the labor, and the present invention aims to solve the problem. It is what

[0004]

The present invention is proposed in order to achieve the above object, and a photoelastic gauge is attached to the surface of an object to be stress-measured, and light passing through a polarizing plate is applied to the photoelastic gauge. The reflected light is captured by an electronic camera through a polarizing plate, the RGB signals of the electronic camera are input to an arithmetic processing device, and the amount of change in the RGB signal is converted into a strain amount of the photoelastic gauge by the arithmetic processing device. , An optical stress measuring method for obtaining stress from the strain amount, and a stress optical measuring method for automatically controlling the stress by automatically controlling the operation of the photographing device and the arithmetic processing device such as the electronic camera by a controller. Is provided.

[0005]

[Function] Irradiates the photoelastic gauge with light that has passed through the polarizing plate,
If you observe the reflected light with an electronic camera through a polarizing plate,
The hue of the photoelastic gauge changes depending on the strain amount of the photoelastic gauge. The hue changes depending on the rotation angle of the polarizing plate,
The strain amount of the photoelastic gauge can be measured by knowing the displacement of the polarization rotation angle. The hue of the output signal of the electronic camera also changes in accordance with the hue change of the photoelastic gauge. The stress at the portion where the photoelastic gauge is attached is measured from the strain amount.

According to a second aspect of the present invention, in addition to the above-described operation, the operations of the photographing device such as an electronic camera and a light source and the operation device are controlled by the control device, and the measurement and the operation processing are automatically performed according to the set program. Be seen.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes an electronic camera such as a so-called floppy camera or video camera for still image shooting, which can output an image signal as an RGB signal. The electronic camera 1 has a built-in autofocus mechanism, a polarizing plate 3 and a 1/4 wavelength plate 4 are attached to the tip of the zoom lens 2, and an electric mechanism 5 can perform zooming and rotation of the polarizing plate 3. A light source 6 such as a spotlight is attached to the upper part of the electronic camera 1, and a polarizing plate 7 and a 1/4 wavelength plate 8 are attached to the front surface of the light source 6. The electronic camera 1 is mounted on an electric pan head 9 driven by a motor, and can swing freely vertically and horizontally. The electric pan head 9 has a control device 10 built-in, and controls a pan operation according to a command from a computer 11 described later.

The RGB signals output from the electronic camera 1 are converted into digital signals by the A / D converter 13 of the video camera input device 12 and written in the frame memory 14 as image information. The written image information is reproduced on the screen of the monitor CRT 15, and the computer 11 performs arithmetic processing to obtain hue coordinates, and the arithmetic result can be displayed graphically or numerically on the CRT 16. Instructions to the computer 11 are inputted by the keyboard 17 and the mouse 18, and the position control of the electric pan head 9, the turning on / off and zooming of the electronic camera 1, the rotation of the polarizing plate 3 and the turning on / off of the light source 6 are all performed from the computer 11. And control signal RS-2
Cable 1 via 32C interface (not shown)
Inputs are made to the respective control devices 1a and 10 of the electronic camera 1 and the electric pan head 9 by means of 9 and 20.

21 are photoelastic gauges attached to the surface of a structure such as a tunnel lining body. Photoelastic gauge 2
1,21 ... are usually 1 cm wide, 5 cm long, 5-6 m thick
m, and both ends in the length direction are attached to a structure (not shown) with an adhesive. Next, the procedure for measuring the amount of stress strain of a structure will be described with reference to the flowchart of FIG. First, as a pre-measurement step, the photoelastic gauge 21 is attached in advance to the same material as the target structure, and the light from the light source is passed through the polarizing plate and projected onto the photoelastic gauge 21. Then, the reflected light of the photoelastic gauge 21 is captured by the electronic camera 1 and displayed on the monitor CRT 15. The photoelastic gauge 21 exhibits a purple color when no stress is applied, but when it does not exhibit a purple color when it is attached to the measurement point, a control signal is sent to the control device 1a of the electronic camera 1 by operating the keyboard 17. Output and rotate the polarizing plate 3 to rotate the photoelastic gauge 2 on the screen.
Make 1 appear purple. The turning position of the polarizing plate 3 at this time is stored in the computer 11 as a reference angle. After that, when a certain stress is applied to the object to generate strain, the color of the photoelastic gauge 21 on the screen changes. RGB of the image area of the photoelastic gauge 21 at this time
The hue vector coordinates of the input signal and the stress strain amount are stored, and the stress is changed in several stages to collect data. Then, a correspondence table of stress and strain amounts and hue coordinates is generated by the calculation of the computer 11, and this is stored in the storage device of the computer 11 as a correspondence table (10
1).

In addition, the electronic camera 1 is installed at the measurement location,
By operating the electric pan head 9 and the electric mechanism 5 of the electronic camera 1 with the keyboard 17 or the mouse 15, any one of the photoelastic gauges 21, 21, ... Shown in FIG. 1 is enlarged to a predetermined size on the screen of the monitor CRT 15. Project at a rate. When the color of the photoelastic gauge 21 projected on the screen is not purple, the polarizing plate 3 is rotated to match the hue coordinate of purple. Then, the control amounts of the electric pan head 9, the electric mechanism 5, and the polarizing plate 3 at this time are stored in the computer 11. This operation is performed for all the photoelastic gauges 21, 21, ... (102).

Then, the program of the measuring order and the measuring time of each photoelastic gauge 21, 21, ... Is inputted to the computer 11 (103). When the execution of the process is started thereafter, the computer 11 activates the electronic camera 1 and the light source 6 at a predetermined time and controls the electric pan head 9. Then, the optical axis of the electronic camera 1 is made to coincide with the photoelastic gauge 21 designated by the program, and a predetermined zoom operation is performed to store the captured image signal in the frame memory 14. Then, the hue coordinate of a predetermined image area in the stored image signal is calculated, the strain amount and the stress corresponding to the hue coordinate are read from the correspondence table written in the storage device, and this is stored in the storage device as measurement data. Write (104).

The above-described work is sequentially performed until the end according to the measurement program, and the data of the hue coordinate, strain and stress of each measurement point is accumulated. After the measurement is completed or during the measurement, the data stored in the computer can be displayed on the CRT 16 or can be taken out from the printer as a hard copy (105). It is also possible to send data online to a remote computer room to centrally process and manage data at multiple sites (106).

The stress calculation method may be the following method. First, the correspondence table between the rotation amount of the polarizing plate 3 and the change of the hue coordinate is set in the computer 11. Then, the hue coordinate of the input RGB signal is obtained, and the rotation amount N of the polarizing plate from the purple hue coordinate which is the reference is obtained from the correspondence table. From the rotation amount N, the strain ε and the stress σ can be obtained by the following equations.

[0014]

[Equation 1] As described above, it is possible to automatically collect a large amount of measurement data, perform data processing and management, and perform arbitrary measurement at any time by operating the keyboard. still,
The configuration of the measuring device, the method of calculating the stress, and the like are not limited to the present embodiment, and various modifications can be made, and it goes without saying that the present invention extends to those modified.

[0015]

As described in detail in the above-mentioned one embodiment, the present invention optically measures the stress and strain of the structure, so that the structure between the target structure and the measuring device is made wireless. Wiring work is unnecessary, and materials and labor are reduced. Also,
Since the measurement work is automatically performed, the stress measurement work in the dangerous area can be unmanned and the risk of an accident can be eliminated. Further, the labor of measurement work for a long time can be remarkably reduced, a large amount of data can be processed, and a remarkable effect can be exerted on labor saving.

[Brief description of drawings]

FIG. 1 is a block diagram of a stress measuring device.

FIG. 2 is a flowchart showing a stress measurement process.

[Explanation of symbols]

 1 Electronic Camera 3,7 Polarizing Plate 4,8 1/4 Wave Plate 6 Light Source 11 Computer 14 Frame Memory 21 Photoelastic Gauge

Claims (2)

[Claims] 1. A photoelastic gauge is attached to the surface of an object to be stress-measured, the photoelastic gauge is irradiated with light passing through a polarizing plate, and the reflected light is captured by an electronic camera through the polarizing plate. A method for optically measuring stress by inputting a signal to an arithmetic processing unit, converting the amount of change of the RGB signals into a strain amount of a photoelastic gauge by the arithmetic processing unit, and obtaining stress from the strain amount. 2. The optical stress measuring method according to claim 1, wherein the operation of the photographing device such as the electronic camera and the arithmetic processing device is program-controlled by a control device to automatically perform stress measurement.